A wastewater reuse treatment method

Abstract

This invention discloses a wastewater reuse treatment method, comprising the following steps: S1, mixing wastewater, biological agents, alkali, and flocculant I, and performing solid-liquid separation to obtain supernatant I and bottom sludge I; S2, concentrating supernatant I to obtain product water I and product water II; S3, mixing product water II, modified bottom sludge I, and flocculant II for crystallization treatment, and performing solid-liquid separation to obtain supernatant II and bottom sludge II. This invention employs a concentration treatment method for supernatant I, concentrating the sulfate-based salts in the wastewater into product water II, and then separating the calcium sulfate-based salts from the wastewater through crystallization products. This invention avoids the reagent consumption and energy consumption of the dual-alkali method in traditional pretreatment-membrane-evaporation processes, resulting in low treatment costs and high open-circuit efficiency.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a wastewater reuse treatment method. Background Technology

[0002] In typical non-ferrous metal mining, smelting, and processing processes, large amounts of wastewater containing heavy metals are generated. Furthermore, due to the transformation of sulfur in sulfide ores in the non-ferrous metal industry, a large amount of sulfate ions are also present in the wastewater, forming a sulfate-based heavy metal wastewater system. The conventional treatment requirement for this type of wastewater is deep removal of heavy metals, commonly employing processes such as sulfidation, neutralization, and flocculation. Among these, neutralization is the lowest cost and most frequently used. Neutralizing agents commonly used are calcium carbonate and calcium hydroxide. The introduction of calcium ions into the neutralizing agent increases the saturation of calcium sulfate in the wastewater. Wastewater containing saturated calcium sulfate will cause scaling and blockage of pipelines and equipment during discharge and reuse. This is especially problematic in reuse applications with specific requirements for scaling and salt content, such as cooling water, circulating water, and process water. Reusing wastewater containing salt, sulfate, and calcium will negatively impact equipment performance and process parameters.

[0003] To completely remove salts, sulfates, and other components from wastewater, a conventional approach is a pretreatment-membrane-evaporation combined process. Pretreatment removes components that negatively impact membrane operation, such as using a dual-alkali method to remove calcium and magnesium ions and flocculation to remove fluoride ions. The pretreated effluent then enters the membrane concentration process, with the resulting freshwater reused. The salts in the wastewater are primarily absorbed into the membrane concentrate, where they are subsequently removed from the wastewater system as crystals through evaporation. This treatment process consumes a large amount of reagents in the dual-alkali method and consumes significant amounts of heat, steam, and electricity during evaporation. While it thoroughly removes anions and cations, it suffers from a long process flow, high reagent dosage, and high operating costs.

[0004] Therefore, it is necessary to develop a heavy metal wastewater reuse treatment method that is simple in process, low in treatment cost, and has an open-circuit efficiency that meets the usage requirements. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the first aspect of the present invention proposes a method for treating and reusing heavy metal wastewater, which has a simple process, low treatment cost, and open-circuit efficiency that meets the application requirements.

[0006] A method for treating and reusing heavy metal wastewater according to a first aspect of the present invention includes the following steps:

[0007] S1. Wastewater, biological agents, alkali and flocculant I are mixed and separated into supernatant I and bottom sludge I.

[0008] S2. The supernatant I is concentrated to obtain product water I and product water II;

[0009] S3. Mix the permeate II, the modified bottom sludge I, and the flocculant II, and perform crystallization treatment and solid-liquid separation to obtain supernatant II and bottom sludge II;

[0010] The raw materials for the biological agent include bacterial broth obtained from chemoautotrophic bacteria culture; and iron salts or ferrous salts;

[0011] The modified bottom slag I is prepared by the following method:

[0012] (1) Filter the bottom residue I to obtain filter bottom residue I; mix and stir filter bottom residue I, limestone powder, sawdust powder and sulfuric acid to obtain the precursor;

[0013] (2) The precursor is granulated, roasted, cooled and crushed to obtain the modified bottom residue I.

[0014] The wastewater reuse treatment method according to embodiments of the present invention has at least the following beneficial effects:

[0015] This invention first mixes wastewater, biological agents, alkali and flocculant for degravation treatment to obtain supernatant I and bottom residue I. Supernatant I is then concentrated to obtain product water I and product water II. Product water II and modified bottom residue I are then crystallized to obtain supernatant II.

[0016] This invention employs a concentration process for the supernatant I, concentrating the sulfate-rich salts from the wastewater into the product water II. Then, through crystallization, the calcium sulfate-rich salts are separated from the wastewater as crystallized products. This invention avoids the reagent consumption and energy consumption of the dual-alkali method in traditional pretreatment-membrane-evaporation processes, resulting in low treatment costs.

[0017] Furthermore, this invention modifies the bottom slag I from the biological agent degrafting treatment by combining it with limestone powder, sawdust, and sulfuric acid. This achieves both internal system reuse of the bottom slag as solid waste and improved crystallization efficiency through modification. During the modification process, the bottom slag I and limestone powder, under the regulation of sulfuric acid, form a large number of active iron, calcium, and other metal ions. After mixing with sawdust and undergoing sintering and pulverization, the modified bottom slag I exhibits characteristics such as multiple functional groups, high porosity, and high specific surface area. In the subsequent crystallization process, the active functional groups such as iron, calcium, and sulfate on the surface can efficiently adsorb calcium and sulfate ions in the wastewater, disrupting the charge balance between ions in small regions and forming a chain-like induction effect, significantly improving the salt solid-liquid open-circuit efficiency during crystallization.

[0018] According to a preferred embodiment of the present invention, the wastewater contained in the present invention includes sulfate ions and heavy metal ions.

[0019] According to a preferred embodiment of the present invention, the mass ratio of the filter press residue I, limestone powder, sawdust and sulfuric acid is (6-10):(2-3):(1-3):1.

[0020] According to a preferred embodiment of the present invention, the hydrogen ion concentration in the sulfuric acid is 10. -3 ~10 -5 mol / L.

[0021] According to a preferred embodiment of the present invention, the biological agent is prepared by the following method:

[0022] a. The chemoautotrophic bacteria were cultured in 9K medium supplemented with FeSO4·7H2O to obtain the bacterial solution;

[0023] b. The bacterial culture obtained in step a is reacted with iron or ferrous salt to obtain a biological agent.

[0024] According to a preferred embodiment of the present invention, the chemoautotrophic bacteria include *Thiobacillus ferrooxidans* or *Thiobacillus thiooxidans*.

[0025] According to a preferred embodiment of the present invention, the dosage of the biological agent is 0.1 to 2.4 g / L.

[0026] According to a preferred embodiment of the present invention, the alkali includes at least one of calcium hydroxide and sodium hydroxide.

[0027] According to a preferred embodiment of the present invention, flocculant I and flocculant II are independently selected from at least one of PAM, polyaluminum chloride, and polyferric chloride.

[0028] According to a preferred embodiment of the present invention, the concentration of the alkali is 0.5 to 5 g / L.

[0029] According to a preferred embodiment of the present invention, the amount of flocculant II and flocculant II added is independently selected from 1 to 50 g / m³. 3 .

[0030] According to a preferred embodiment of the present invention, in step S2, the concentration process includes at least one of reverse osmosis concentration, electrodialysis concentration, and thermal concentration.

[0031] According to a preferred embodiment of the present invention, the particle size of the pulverized product is 1.7 μm to 30 μm.

[0032] According to a preferred embodiment of the present invention, the roasting temperature is 400°C to 900°C.

[0033] According to a preferred embodiment of the present invention, the roasting time is 15 to 60 minutes.

[0034] According to a preferred embodiment of the present invention, in step (1), the stirring speed is 2000-5000 r / min; the stirring time is 30-60 min.

[0035] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0036] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0037] Figure 1 This is a flowchart of the processing in Embodiment 1 of the present invention;

[0038] Figure 2 This is a processing effect diagram of Embodiment 1 of the present invention;

[0039] Figure 3 This is a processing effect diagram of Embodiment 2 of the present invention;

[0040] Figure 4 This is a diagram showing the processing effect of Comparative Example 1 of the present invention. Detailed Implementation

[0041] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0042] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0043] The raw materials used in the embodiments and comparative examples of this invention are as follows:

[0044] Biological agent: prepared according to Example 1 of patent CN 104478160 A.

[0045] Alkali: Lime milk; commercially available.

[0046] Flocculant: PAM; commercially available.

[0047] The formula for calculating the open circuit rate is: (influent concentration - effluent concentration) / influent concentration * 100%.

[0048] TDS testing: Leici DZS-706F multi-parameter analyzer.

[0049] The ion concentrations of each substance were determined by ion chromatography.

[0050] Example 1

[0051] This example provides a wastewater reuse treatment method; the unit treatment cost is approximately 6.2 yuan / m³. 3 The processing flow diagram is as follows: Figure 1 As shown, the steps are as follows:

[0052] S1. Wastewater from a lead-zinc mine is treated in a gravity removal reactor by adding 0.5 g / L of biological agent, 1.1 g / L of calcium hydroxide, and 3 g / m³ of other chemicals. 3 PAM was used for weight removal to obtain supernatant I and bottom residue I;

[0053] S2. The supernatant I is concentrated by reverse osmosis with a reverse osmosis feed water pressure of 1.4 MPa and a product water rate of 75% to obtain product water I and product water II.

[0054] S3. In the crystallization reaction tank, add 3g / m of the modified bottom slag I. 3 PAM and permeate II are subjected to crystallization treatment; solid-liquid separation yields supernatant II and bottom residue II.

[0055] The modification treatment method for bottom slag I is as follows: Mix filter press bottom slag I, limestone powder, sawdust, and dilute sulfuric acid in a mass ratio of 7:2:1:1. The concentration of dilute sulfuric acid is 10% hydrogen ion content. -4 The product was processed by stirring, granulation, calcination, cooling, and pulverization. The stirring speed was 3000 r / min, the stirring time was 30 min, the calcination temperature was 800℃, the calcination time was 30 min, and the particle size of the pulverized product was ≤13 μm.

[0056] Product water I is used directly as recycled water, while supernatant II is returned to the degravity treatment reactor.

[0057] The ion concentrations of wastewater and treated reclaimed water are shown in the figure. Figure 2 ;from Figure 2 It can be seen that the TDS of the wastewater (raw water) is as high as 3930 mg / L; the TDS of product water I is 182 mg / L, the calcium ion concentration is less than 10 mg / L, the sulfate ion concentration is less than 50 mg / L, and the open circuit rate is 99%, which can meet the "Water Quality Standard for Reclaimed Water for Circulating Cooling Water" (HG / T3923-2007) and meet the reuse requirements of equipment cooling water and other water with high water quality requirements.

[0058] Example 2

[0059] This example provides a wastewater reuse treatment method; the unit treatment cost is approximately 6.0 yuan / m³. 3 The steps are as follows:

[0060] S1. Wastewater from a lead-zinc mine is treated in a gravity removal reactor by adding 0.5 g / L of biological agent, 1.15 g / L of sodium hydroxide, and 40 g / m³ of other chemicals. 3 Polyaluminum chloride is subjected to a gravimetric removal process to obtain supernatant I and bottom residue I;

[0061] S2. The supernatant I is concentrated by reverse osmosis with a reverse osmosis feed water pressure of 1.25 MPa and a product water rate of 77% to obtain product water I and product water II.

[0062] S3. In the crystallization reaction tank, add 50 g / m³ of modified bottom slag I. 3 Polyferric chloride is crystallized; solid-liquid separation yields supernatant II and bottom residue II.

[0063] The modification treatment method for bottom slag I is as follows: Mix filter press bottom slag I, limestone powder, sawdust, and dilute sulfuric acid in a mass ratio of 7:2:1:1. The concentration of dilute sulfuric acid is 10% hydrogen ion content. -4 The concentration was mol / L, and the product underwent stirring, granulation, calcination, cooling, and pulverization. The stirring speed was 3000 r / min, the stirring time was 30 min, the calcination temperature was 800℃, the calcination time was 30 min, and the particle size of the pulverized product was ≤13 μm.

[0064] Permeate I and supernatant II are combined and used as recycled water. Ion concentrations of the wastewater and treated recycled water are shown in [reference needed]. Figure 3 The TDS content of the reclaimed water is 1832 mg / L, the calcium ion open circuit rate is 75%, and the sulfate ion open circuit rate is 77%, which can meet the reuse requirements of circulating water, flushing water, and other waters with low water quality requirements.

[0065] Comparative Example

[0066] This example provides a wastewater reuse treatment method; the steps are as follows:

[0067] S1. Wastewater from a lead-zinc mine is treated in a gravity removal reactor by adding 0.5 g / L of biological agent, 1.15 g / L of lime slurry, and 3 g / m³ of other chemicals. 3 PAM was used for weight removal to obtain supernatant I and bottom residue I;

[0068] S2. The supernatant I is concentrated by reverse osmosis with a reverse osmosis feed water pressure of 1.25 MPa and a product water rate of 77% to obtain product water I and product water II.

[0069] S3. In the crystallization reaction tank, add product II; and add 3g / m 3PAM was subjected to crystallization; solid-liquid separation yielded supernatant II and bottom residue II.

[0070] Permeate I and supernatant II are combined to obtain recycled water. The ion concentrations of the raw wastewater and the treated recycled water are shown in the figure. Figure 4 ;from Figure 4 It can be seen that the TDS content of the combined reclaimed water is 3472 mg / L, the calcium ion open circuit rate is only 28%, and the sulfate ion open circuit rate is only 22%. Compared with Example 2, the treatment effect is significantly worse and it cannot be used for reclaimed water.

[0071] The present invention has been described in detail above with reference to the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A wastewater reuse treatment method, characterized in that, Includes the following steps: S1. Wastewater, biological agents, alkali and flocculant I are mixed and separated into supernatant I and bottom sludge I. S2. The supernatant I is concentrated to obtain product water I and product water II; S3. Mix the permeate II, the modified bottom sludge I, and the flocculant II, and perform crystallization treatment and solid-liquid separation to obtain supernatant II and bottom sludge II; The raw materials for the biological agent include bacterial broth obtained from chemoautotrophic bacteria culture; and iron salts or ferrous salts; The modified bottom slag I is prepared by the following method: (1) Filter the bottom residue I to obtain filter bottom residue I; mix and stir the filter bottom residue I, limestone powder, sawdust and sulfuric acid to obtain the precursor; the mass ratio of the filter bottom residue I, limestone powder, sawdust and sulfuric acid is (6-10):(2-3):(1-3):1; (2) The precursor is granulated, roasted, cooled and crushed to obtain the modified bottom residue I; The roasting temperature is 400℃~900℃.

2. The wastewater reuse treatment method according to claim 1, characterized in that, The hydrogen ion concentration in the sulfuric acid is 10. -3 ~10 -5 mol / L.

3. The wastewater reuse treatment method according to claim 1, characterized in that, The biological agent is prepared by the following method: a. The chemoautotrophic bacteria were cultured in 9K medium supplemented with FeSO4·7 H2O to obtain the bacterial solution; b. The bacterial culture obtained in step a is reacted with iron or ferrous salts to obtain a biological agent.

4. The wastewater reuse treatment method according to claim 1, characterized in that, The dosage of the biological agent is 0.1~2.4 g / L.

5. The wastewater reuse treatment method according to claim 1, characterized in that, The alkali includes at least one of calcium hydroxide and sodium hydroxide.

6. The wastewater reuse treatment method according to claim 1, characterized in that, The flocculant I and flocculant II are independently selected from at least one of polyacrylamide, polyaluminum chloride, or polyferric sulfate.

7. The wastewater reuse treatment method according to claim 1, characterized in that, In step S2, the concentration process includes at least one of reverse osmosis concentration, electrodialysis concentration, and thermal concentration.

8. The wastewater reuse treatment method according to claim 1, characterized in that, The particle size of the pulverized product is 1.7μm to 30μm.

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